ERDF Implementation and Evaluation

SQL, Prolog, RDF and OWL are among the most prominent and most widely used computational logic languages. SQL, Prolog and RDF do not allow to represent negative information, only OWL does so. RDF does even not include any negation concept. While SQL and Prolog only support reasoning with closed predicates based on negation-as-failure, OWL supports reasoning with open predicates based on classical negation, only. However, in many practical application contexts, one rather needs support for reasoning with both open and closed predicates. To support this claim, we show that the well-known Web vocabulary FOAF includes three kinds of predicates, which we call closed, open and partial predicates. Therefore, reasoning with FOAF data, as a typical example of reasoning on the Web, requires a formalism that supports the distinction between open and closed predicates. We argue that ERDF, an extension of RDF, offers a solution to deal with this problem. Keyword List Rule, Reasoning, JenaRules, RDF(S), ERDF, SPARQL, FOAF. Project co-funded by the European Commission and the Swiss Federal Office for Education and Science within the Sixth Framework Programme.